Inequalities for the norms of vector functions in a spherical layer

Abstract

We consider the vector functions in a domain homeomorphic to a spherical layer bounded by twice continuously differentiable surfaces. Additional restrictions are imposed on the domain, which allow to conduct proofs using simple methods. On the outer and inner boundaries, the normal and the tangential components of the vector are zero, respectively. For such functions, the integral over the domain of the squared vector is estimated from above via the integral of the sum of squared gradients of its Cartesian components. The last integral is estimated through the integral of the sum of the squared divergence and rotor. These inequalities allow to define two norms equivalent to the sum of the norms of the Cartesian components of vector functions as the elements of the space $W_2^{(1)}(\Omega)$. The integrals over the boundaries of the squared vector are also estimated. The constants in all proved inequalities are determined only by the shape of the domain and do not depend on a specific vector function. The inequalities are necessary for investigating the operator of a mixed elliptic boundary value problem.